Creating a template from cloud init image

OS: Arch

To simplify and speed up the process of VMs deployment on local machine I will use cloud init image. We can find them all around the place. For my tasks I need to use ubuntu 20.04 server.

Source of the image can be found: cloud-images

Dependencies:

• libvirt
• qemu
• virt-manager
• bridge-utils
• cloud-utils

sudo pacman -Syy
sudo pacman -S qemu libvirt virt-manager virt-viewer bridge-utils cloud-utils curl
sudo usermod -aG libvirt $(whoami)
sudo systemctl enable --now libvirtd

Downloading image

The standard path for libvirt to store the images is /var/lib/libvirt/images.

Downloading latest focal version of ubuntu.

sudo curl -L https://cloud-images.ubuntu.com/focal/current/focal-server-cloudimg-amd64.img -o /var/lib/libvirt/images/focal-server-cloudimg-amd64.img

Adding ssh keys

While configuring cloud-init we will need to provide ssh public keys

ssh-keygen -t rsa -b 4096 -C "[email protected]"

Save this file in ~/.ssh/ci_ubuntu, where ci is for cloud init and ubuntu for user name

Creating cloud init configuring

1. Create a directory cloud-init-config at /var/lib/libvirt/images

2. Enter the directory and create 2 files:

   • cloud-config

   ( echo "#cloud-config
       users:
         - name: ubuntu
           gecos: Ubuntu
           sudo: ALL=(ALL) NOPASSWD:ALL
           groups: users, admin
           shell: /bin/bash
           ssh-authorized-keys:
             - $(cat <PATH_TO_YOUR_PUB_KEY>.pub)
       
       # Enable password authentication with the SSH daemon
       ssh_pwauth: False
       write_files:
         - path: /etc/netplan/01-netcfg.yaml
           content: |
             network:
               version: 2
               ethernets:
                 all:
                   match:
                     name: \"en*\"
                   dhcp4: true" ) > cloud-config

   • user-data

   touch user-data

3. The last one - use cloud-localds to create iso image. Run in cloud-init-config directory

   cloud-localds ubuntu-cloud-init.iso cloud-config user-data

Creating VM which we will use as template

Using virt-manager:

1. Create new virtual machine -> Import existing disk image -> -> Set your resources -> Set check box "Customize configuration before install" and select network (NAT)
2. Add hardware -> Device type: CDROM -> Select or create custom image: /var/lib/libvirt/images/cloud-init-config/ubuntu-cloud-init.iso
3. Boot options -> Select CDROM and move it on top
4. Begin installation

Init ssh to template

1. Get your template IP.

sudo virsh list --all
sudo virsh domifaddr <your_template_vm_name>

2. SSH to your template using cloud init credentials:

ssh -i ~/.ssh/ci_ubuntu ubuntu@YOUR_VM_IP_ADDRESS

3. Update, install qemu agent

sudo agt-get udpate && apt-get install qemu-guest-agent -y
sudo systemctl enable qemu-guest-agent --now

4. Clean your image

sudo cloud-init clean

5. Delete your machid-id data

sudo truncate -s 0 /etc/machine-id
sudo rm /var/lib/dbus/machine-id
sudo ln -s /etc/machine-id /var/lib/dbus/machine-id

6. Shutdown

sudo shutdown now

Tweaking permissions

While it is a template - you can still run it which will lead to mailfunction. To prevent this - we will set privilages to 400

sudo chmod 400 /var/lib/libvirt/images/focal-server-cloudimg-amd64.img